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2020 Chemical accident in USA with chlorine
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General accident information
Class/Quality * * * * *
Year 1978
Summary Derailment of 44 tankwagons
Caused by sabotage caused
Big chlorine release
Country USA
Location RAILWAY
Chemicals Ammonium nitrate (liquid), Caustic soda (liquid), Caustic soda (liquid), Chlorine,
Chlorine, Lpg, Turpentine
Cause Sabotage/Vandalism/Terrorism
Fatalities/Injuries 8 / 153
Occurrences or events Burst/Rupture, Chemical reaction, Chemical reaction, Derailment,
Derailment, Dismount/Disconnect, Disperse/Spread, Drive,
Evacuation, Fire fighting/Emergency response, Jack-knife, Mechanical failure,
Mount/Connect, Penetrate/Puncture, Pollution/Contamination, Release,
Remove, Remove, Safety-measures, Traffic-interruption,
Vaporize, Wrong-action, Wrong-composition
Full accident information 
download accident report Click here to view a document containing the full accident information

Date : 1978 0226

Eight drivers of private cars on a nearby highway were killed and a further 138 were injured when a tankwagon containing 90E+3/kg of liquefied chlorine gas was ruptured in an incident that involved the derailment of 44 wagons of a five-locomotive, 140-wagon train. When the lead locomotive suddenly lurched off the track the driver applied the emergency brakes but had no time to warn the crew at the rear of the train. Because of the time of the day and the general weather conditions, which included fog in the area, there was little or no wind and the escaping chlorine was not dispersed to any significant degree.
The tankwagon containing chlorine jack-knifed as a result of a secondary derailment releasing a cloud of gas which obscured a nearby highway and caused the dead of motorists who were unable to escape. Emergency response teams from CHEMTREC, contacted some hours after the initial incident, were able to advise the local authorities to neutralize the remaining contents of the tankwagon with caustic soda.
The resultant large, slowly dispersing chlorine cloud drifted to a nearby highway and choked car engines. The cause was sabotage, bolts had been removed from a section of track and rail was pulled aside. The next day a pit was dug to neutralize the remaining chlorine with caustic soda and water. The tankwagon was moved to the side of the pit. A day later the chlorine was moved in the pit and neutralized with the caustic soda and water. There was still 1000-2000/kg left in the wagon. Now was decided to spray water into the tank to let it react with the chlorine. A plume came out of the wagon and heat occurred. After 15 minutes it was over.

Respiratory health following acute chlorine exposure by University School of Medicine, New Orleans, Louisiana.

153 persons were exposed. 8 persons died, 23 required hospital admission, 25 others had signs of respiratory abnormality, and 97 lacked such signs.
113, including 20 of 23 admitted and 21 of 25 others with respiratory abnormality, were tested, 102 on multiple occasions. All subjects were examined in area hospitals for respiratory effects, within 48 hours of exposure, and their "triage status" was used to categorize for degree of acute chlorine injury. 64 adults tested 3 weeks after exposure, had normal mean lung function with expected smoking differences, but no difference according to distance from spill or triage status. Testing was repeated annually, and 60 adults had a suitable number and separation of data points to examine the course of longitudinal change.
Linear declines in lung function over six years were available. These values also showed expected differences for smoking, but none for distance from spill or triage category. The University School of Medicine concluded that chlorine injury had no discernible effect on early post-exposure lung function, or annual change over the subsequent six years.

The National Transportation Safety Board (NTSB) determined that the probable cause of the derailment was the intentional displacement of a rail end into the guideway reserved for the wheel flange. The rail end was restrained in this abnormal position until the train derailed. A rail road tanker car of liquid chlorine was punctured in the derailment when struck by the corner of another car, and its contents were released. All of the injuries and death were the result of chlorine inhalation.

No deviations from FRA Safety Standards were noted with regard to track structure or track geometry.
No evidence of any material failure of any component which could be considered contributory to the cause of this derailment could be found.
The train was being operated in accordance with applicable rules and regulations of the railroad and the Federal Railroad Administration (FRA).
The absence of any scuff marks on the left front wheel tread of the locomotive indicated that the wheel had not been derailed for any distance.
The cut mark across the flange of the left front wheel was made when the flange struck a rail end at speed.
The damaged rail end, which was found at or near the determined point of derailment, exhibited a metal deposit on the field side of the head of the rail.
The metal was sheared off where it was struck by a wheel flange at speed.
The damaged rail end displayed metal deposits on the bottom of the rail head on the gage side.
This metal could not have been displaced if the joint bars had been in place.
Joint bars and bolts were not in place on the rail end when the train derailed.
In order for the wheel flange to shear the metal off of the field side of the rail, the rail end must be set on the direct path of the wheel flange.
The rail end was forcibly held in this abnormal position until struck by the wheel flange.
Thirty minutes elapsed from the time of the derailment until emergency forces were notified.
Top and bottom shelf couplers would have helped to keep the train more in line with the tracks, reducing the likelihood of jack-knifing and minimizing the puncture.
The railroad tanker cars loaded with hazardous materials in the forward portion of the train were exposed to high kinetic forces from the abrupt stopping of the locomotive and the unequal braking capabilities of the cars in the train.

Lesson learned (measures for prevention)
Use top and bottom shelf couplers, head shields and insulation also for DOT 105 tankwagons. (Class I, Urgent Action) (R-75-58)
Investigate the safest arrangement of the wagons in a freighttrain for the transport of Hazardous chemicals. (Class II, Priority Action) Regulations for adequate braking arrangements must be issued. (R-78-59)
The railway company must maintain radio communications between trains and a base station around the clock. (Class I, Urgent Action) (R-78-57)

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